Adjustable and modular backplane assembly for providing a fiber-optics communication backplane

ABSTRACT

A modular and adjustable backplane assembly for providing a fiber-optics backplane interface to a plurality of router cards functioning as a data router is provided. The assembly includes a first portion having a first array of connectors for interfacing with a compatible array of second connectors engaging specific ones of the router cards, and a second portion having a second array of connectors for interfacing with a compatible array of second connectors engaging specific others of the router cards. The mechanics of the assembly enable a moveable attachment with respect to the first and second portions such that they may be positionally adjusted during mounting, and wherein external data paths are provided from individual ones of the connectors to individual others of the connectors by fiber-optic conductors.

CROSS-REFERENCE TO RELATED DOCUMENTS

The present application is a continuation application of patentapplication Ser. No. 10/386,883 entitled “Adjustable and ModularBackplane Assembly for Providing a Fiber-Optics CommunicationBackplane,” filed on Mar. 11, 2003 now U.S. Pat. No. 6,761,487, which isa continuation of Ser. No. 09/920,556 filed Jul. 31, 2001 (U.S. Pat. No.6,533,463, issued Mar. 14, 2003), which are incorporated in theirentirety by reference.

FIELD OF THE INVENTION

The present invention is in the field of backplane communication andpertains more particularly to a fiber-optics backplane for a scalablerouter.

BACKGROUND OF THE INVENTION

In the general state of the art of electrical and electronic systemshoused in cabinets (often termed chassis), there are typically inputsand outputs to the system, facilitated by connection of communicationlinks of various sorts, over which signals are received and sent. Thereare also numerous situations wherein groups of components in a chassishave to be connected to and communicate with other groups of componentsinternally. Data routers in packet networks, such as the well-knownInternet, are a good example. In description in this specification adata router is used as a specific example of such a situation, and thepresent invention in several aspects is applicable to such routers.

Transmission of network data traffic is accomplished with the use ofdata routers as introduced above. A physical data routing machinetypically consists of a processing unit or multiple units which arehoused in a chassis and which communicate with each other and with otherdata routing machines.

In prior art, one method for achieving communication between processingunits in a single chassis, such as in a data router, involves the use ofan electrical backplane. When communication between multiple chassis isrequired, the electrical backplanes of the chassis have been connectedby cables. The electrical backplane is commonly implemented as a printedcircuit board assembly which provides electrical connectivity betweenprocessing units.

Noting that it may sometimes be desirable to communicate at backplanelevel between elements that are not closely physically associated, suchas between elements that may be mounted in separate physical electroniccabinets, there is a potential problem with electrical backplanes. Whenan electrical signal is transmitted over relatively long distances, forexample, deterioration of the signal may occur for any of severalreasons. For example, longer signal paths necessarily present additionalresistance. Also, longer paths present additional opportunity forinterference. Therefore, in order to transmit clean signals in systemsutilizing electrical backplanes the elements in communication must be inrelatively close physical proximity to one another, such as in the samecabinet.

Another drawback to electrical backplane boards is that they arerelatively difficult to service. One reason is that the conductors forthe electrical signals are typically patterned on the board, andindividual conductors (signal paths) cannot be separately serviced. Inmany cases the backplane boards are also hardwired to other components.Because any change or repair is normally via a replacement of the entirebackplane, the system containing the electrical backplane is generallyout of service during any backplane service.

What is clearly needed is an apparatus and method enabling cleaner datasignal transmission between router processing units while at the sametime facilitating easier manufacturing and off-line servicing ofbackplane assemblies.

SUMMARY OF THE INVENTION

In a preferred embodiment of the present invention a modular andadjustable backplane assembly to provide backplane communication betweena first signal interface to a first set of components in a cabinet and asecond signal interface to second set of components in the same cabinetis provided, comprising a first portion mounting a third signalinterface configured to engage the first signal interface, a secondportion mounting a fourth signal interface configured to engage thesecond signal interface, an adjustment mechanism allowing relativemovement between the first and second portions, thereby between thethird and fourth signal interfaces, while preserving the modularity ofthe backplane assembly, and a signal conductor assembly engaging thethird and fourth signal interfaces to communicate signals between thefirst set of components and the second set of components.

In a preferred embodiment the cabinet houses elements of a packetrouter, and the first and second sets of components are router cards. Insome embodiments the first and second signal interfaces are groups ofconnectors for connecting signal conductors to individual ones of thecards in the first and second sets of router cards. Further, the firstand second signal interfaces may be first and second connectors toprinted circuit boards (PCBs) that are in turn connected to the firstand second set of components.

In some cases the third and fourth signal interfaces comprisefiber-optic connectors, and the signal conductor assembly comprises oneor more fiber-optic fibers having end-connectors for engaging thefiber-optic connectors. The fibers may comprise one or more bundles,ribbons or cables.

In some cases the third and fourth signal interfaces comprise electricalconnectors, and the signal conductor assembly comprises one or morecables of electrical conductors having end connectors to engage theelectrical connectors. Also in some cases the signal conductor assemblycomprises a cable of electrical conductors having end-connectors toengage the electrical connectors at the PCBs.

In some embodiments of the backplane assembly the adjustment mechanismcomprises telescopic engagement elements allowing adjustment ofseparation between the first and second portions. The re may further bea locking mechanism for securing the telescoping first and secondportions after adjustment to engage the first and second interfaces.

In other embodiments the adjustment mechanism further comprises firstlocating elements in the immediate area of each of the first and secondsignal interfaces, and compatible locating elements in the immediatearea of the third and fourth signal interfaces, to physically locate thefirst and second portions in assembly to the cabinet to engage the firstand third and the second and fourth signal interfaces. The locatingelements may comprise male and female elements for constrainingengagement position.

In another aspect of the invention a method for connecting a firstsignal interface connected to a first set of components and a secondsignal interface connected to a second set of components in a cabinet,comprising the steps of (a) preparing a modular and adjustable backplaneassembly comprising a first portion mounting a third signal interfaceconfigured to engage the first signal interface, a second portionmounting a fourth signal interface configured to engage the secondsignal interface, an adjustment mechanism allowing relative movementbetween the first and second portions, thereby between the third andfourth signal interfaces, while preserving the modularity of thebackplane assembly, and a signal conductor assembly engaging the thirdand fourth signal interfaces to communicate signals between the firstset of components and the second set of components; and (b) assemblingthe modular backplane assembly to the cabinet, with the third signalinterface engaging the first, and the fourth signal interface engagingthe second, the adjustment mechanism allowing the third and fourthsignal interfaces to assume a proper separation distance to accomplishengagement of the signal interfaces.

In some embodiments the cabinet houses elements of a packet router, andthe first and second sets of components are router cards. In theseembodiments the first and second signal interfaces may be groups ofconnectors for connecting signal conductors to individual ones of thecards in the first and second sets of router cards. Also in someembodiments the first and second signal interfaces may be first andsecond connectors to printed circuit boards (PCBs) that are in turnconnected to the first and second set of components. Further, in someembodiments the third and fourth signal interfaces comprise fiber-opticconnectors, and the signal conductor assembly comprises one or morefiber-optic fibers having end-connectors for engaging the fiber-opticconnectors. The fibers may comprise one or more bundles, ribbons orcables. In some cases the third and fourth signal interfaces compriseelectrical connectors, and the signal conductor assembly comprises oneor more cables of electrical conductors having end connectors to engagethe electrical connectors. Also in some cases the signal conductorassembly comprises a cable of electrical conductors havingend-connectors to engage the electrical connectors at the PCBs.

In some embodiments the adjustment mechanism comprises telescopicengagement elements allowing adjustment of separation between the firstand second portions, and there may further be a locking mechanism forsecuring the telescoping first and second portions after adjustment toengage the first and second interfaces. In addition there may be firstlocating elements in the immediate area of each of the first and secondsignal interfaces, and compatible locating elements in the immediatearea of the third and fourth signal interfaces, to physically locate thefirst and second portions in assembly to the cabinet to engage the firstand third and the second and fourth signal interfaces. The locatingelements may comprise male and female elements for constrainingengagement position.

In another aspect there may be a fifth signal interface connected to oneor both of the third and fourth signal interfaces, the fifth signalinterface placed on the backplane assembly to be accessible with thebackplane assembly mounted to the cabinet, to facilitate connection ofthe backplane assembly to a second backplane assembly having a fifthsignal interface and assembled to a second cabinet, thereby providingsignal communication between components in the first cabinet and thesecond cabinet. The fifth signal interface may be a connector forconnecting one or more signal conductors, and may comprise a fiber-opticconnector compatible with a mating connector for one or more fiber-opticfibers between the backplane assemblies. The fiber-optic fibers can bein one or more ribbons or cables.

In yet another embodiment the fifth signal interface is an electricalconnector compatible with a mating connector of an electrical cablebetween the backplane assemblies.

In embodiments of the invention taught in enabling detail below, for thefirst time an adjustable cabinet backplane is provided to the art, inwhich regions of the backplane may be positioned in assembly accordingto the positions of elements of the cabinet to which the backplane is tobe assembled. Also for the first time an ability to interconnectelements in each cabinet at the backplane level is provided.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 a is a perspective view of a backplane assembly according to anembodiment of the present invention as seen from a first vantage point.

FIG. 1 b is a perspective view of a backplane assembly according to anembodiment of the present invention as seen from a second vantage point.

FIG. 2 is a perspective view of the backplane assembly of FIG. 1 showndisassembled.

FIG. 3 is a block diagram illustrating the relationship between thebackplane assembly of FIGS. 1 and 2 to a main router chassis accordingto an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 a and 1 b are perspective views of a backplane assembly 100according to an embodiment of the present invention as seen from twoseparate vantage points. Backplane assembly 100 comprises separate topand bottom components or portions represented herein as components 105and 106 that can be assembled together and whose clearance tolerancefrom each other can be adjusted via a telescopic or slidable method.Telescopic clearance is illustrated in this example by a bi-directionalarrow labeled Telescopic Clearance. Both components 105 and 106 makingup backplane 100 are, together, mounted to a back panel illustratedherein as back panel 101. Back panel 101 has plurality of openingsprovided therein and adapted for accepting fasteners as may be found incurrent art to secure the connection of backplane assembly or backplane100 to a router chassis.

Referring now to FIG. 1 b, backplane 100 has a plurality of openingsprovided therein and adapted to house a plurality of fabric card (FC)connectors 102. These connectors comprise a communication signalinterface to a set of fabric cards. Connectors 102 are contained inportion 106 of backplane assembly 100. Connectors 102 are, in thisparticular embodiment plastic plug-in connectors arranged in a Cartesianarray, which is designed to match the positions of fabric card terminalsof fabric cards housed in a card cage in a data router chassis (notillustrated). Backplane 100 also has a plurality of line card (LC)fiber-optics connectors 103 provided therein, that comprise anothersignal interface, this time to line cards. Connectors 103 are arrangedin the top portion of backplane assembly 100. Like fabric-cardconnectors 102, they are plastic plug-in connectors. Connectors 103 arearranged in a row matching the pattern of connectors on line cardsinstalled in a main router chassis.

The structure for backplane assembly 100 (portions 105 and 106) may bemanufactured from aluminum, sheet metal, or other durable material thatmay be formed and machined. Similarly, panel 101 may be manufacturedfrom aluminum or other sheet metals.

In this example, backplane connections are implemented using fiberoptics ferrules well-known in the art. In other embodiments of theinvention the connectors on the signal interfaces can be for electricalsignals. Connector housings 102 and 103 function to mechanically houseeither the female or alternatively, the male ferrule. Each ferrulepresents optic strands or fibers, which are strategically aligned by theconnection method so that data may be transmitted between the strands.In actual practice in a preferred embodiment, each connector housing(102, 103) contains 4 optics ferrules either male or female. Cardterminals (not shown) within a router chassis contain 4 ferrules, whichmate with the ferrules in connector housings 102 and 103. If theferrules on the router card terminals are male, then the ferrules on theconnector housings will be female.

Intercommunication between router cards then is facilitated byconnectors 102 and 103 comprising an “optics backplane”. Unlike aphysical electrical backplane board of prior art, fiber strandscomprising communication paths interconnect specific ferrules containedin the housings enabling cross communication among cards housed in themain router chassis. Similarly, ferrules provided in separate routerchassis may be connected by fiber-optics, enabling a fabric card housedin one router chassis to communicate with a similar card housed in aseparate router chassis essentially providing a scalable router. Theimplementation of fiber-optic communication as a backplane enablesmultiple router chassis integrated by backplane communication to formone router to be located much further apart than is practical withprior-art electrical back-planing methods.

In the example of FIG. 1, backplane assembly 100 has 4 alignmentopenings 104 provided therein and adapted to accept alignment pins ordowels (not shown) provided in a main router chassis. Alignment openings104 are strategically located in four strategic locations on thebackplane assembly 100, two on the top portion and two on the bottomportion. Openings 104 are somewhat larger in diameter than thecorresponding diameter of alignment pins or dowels on a router chassis.The oversizing enables acceptance of the alignment pins of a routerchassis without causing misalignment of connectors.

As was described above, backplane assembly 100 in this example consistsof two portions 105 and 106 that are assembled together in a slidablefashion, providing an adjustment mechanism, enabling both vertical andsome horizontal float. When back panel 101 is completely installed tobackplane assembly 100, the slidable position with respect to portions105 and 106 of the assembly is locked. The goal of telescopic capabilityas an adjustment mechanism is to enable alignment openings 104 to beconditionally tolerenced to fit over fixed alignment pins housed in anymain router chassis. It is noted herein that the alignment pins in arouter chassis are associated carefully to the true position of fabricand line card connectors presented for engaging connectors 102 and 103respectively, such that when backplane 100 is adjusted for fit over thealignment pins, all of the optics connections are aligned for plug-in.The dimensional variance may change somewhat from chassis to chassis.Therefore, provision of an adjustable backplane assembly providesmodularity.

FIG. 2 is a perspective view of the backplane assembly 100 of FIGS. 1 aand b shown disassembled illustrating separate components 105 and 106.

This disassembled view illustrates the mechanism of the telescopiccapability of backplane assembly 100. Component or upper portion 105houses connectors 103 while component or lower portion 106 housesconnectors 102. Backplane assembly 100 is illustrated in this examplewithout back panel 101 of FIG. 1 in order to reveal alignment slots thatenable telescopic adjustment. For example, lower portion 106 has 3alignment slots provided therein and labeled “hardware locations”. Thesealignment slots correspond to a matching array (3) of alignment slotsprovided in upper portion 105. Each alignment slot is elongated toprovide the vertical float adjustment described with reference to FIG. 1above. Upper portion 105 may be manufactured of such a width dimensionso as to fit inside portion 106 or so as to fit over portion 106. Thealignment slots are adapted to fit around a common fastening hardwaresuch as bolts.

In one embodiment, metal inserts (not shown) may be used to provide anadjustment mechanism at the location of each alignment slot. Suchinserts are loosened to allow float capability along the elongated slotsuntil suitable match up of alignment openings 104 (FIG. 1) with matchingalignment pins on a router chassis is achieved. With alignmentaccomplished, meaning that openings 104 are successfully mated withcorresponding alignment pins provided in a main router chassis, thetelescopic fasteners can be tightened securing the aligned positioningand backpanel 101 (FIG. 1) may then be installed.

FIG. 3 is a block diagram illustrating the relationship of backplaneassembly 100 to a main router chassis 300 according to an embodiment ofthe present invention. Again, the adjustable backplane assembly invarious embodiments may be for connection of elements in many sorts ofcabinets and systems, of which packet routers are a single example.

Main router chassis 300 houses a card cage 301. Card cage 301 is adaptedto support a line card array 302 and a fabric card array 306. It isnoted herein that line cards 302 and fabric cards 306 of router chassis300 are supported within cage 301 in a fashion similar to books beingstacked along side each other at equal spacing from each other. Eachcard rests in a card slot (not illustrated). The card slots are providedequally spaced from one another, the cards adapted individually to fitsnugly into a designated slot. It is also noted herein that acomparatively few control cards (not illustrated) are, in actualpractice, included in line card array 302.

Exposed Fiber-optics connectors, illustrated herein as fiber-opticsconnectors 303 (for line cards) and fiber-optics connectors 304 (forfabric cards) are in true-position relationship with respect to oneanother when the cards are installed in their respective slots.Fiber-optics connectors 304 and 303 fit easily through provided openingsmachined into or provided in a separate piece like a grate that ismounted onto main router chassis 300. It is noted herein that thepattern of openings provided for fitting card terminals there throughhas all individual openings oversized with respect to inner dimensioningto accept the plastic connector housings in a slip-through fashion.However, the pattern of openings provided on backplane 100 compriseindividual openings that are tightly-toleranced. Each line card andfabric card has, in addition to fiber-optics connectors 304 and 303,connectors 305 to facilitate plug-in connection to conventionalelectrical backplane boards, labeled as such, which are installed inmain chassis 300. It is noted herein that electrical backplanes arestill used in this example for propagating error messaging and othersuch signals.

In various applications the backplane assembly may be implemented as anelectrical backplane or as a fiber-optic backplane. However,fiber-optics is used in this example to transmit information related todata packets from card to card along with certain other message types.Fiber-optics FC and LC connectors provided on housing 100 are analogousto connectors 102 and 103 respectively of FIG. 1. In this example one ormore fiber-optics cables, represented by element number 310, connect theupper and lower signal interfaces (the fiber-optic connectors 102 and103, see FIGS. 1 a and b). This cable or cables are provided withsufficient slack that the necessary adjustment can be made between theupper and lower portions of the backplane assembly. In the case of anelectrical backplane this cable or cables comprise cables of electricalconductors.

In one embodiment, especially useful in an electrical backplane,separate PCBs may be mounted at the upper and lower signal interfaces,and cable connection 310 is accomplished between these PCBs. In thisembodiment the connection PCBs may be considered a part of signalinterfaces 102 and 103.

When backplane assembly 100 is in a loosened and vertically-adjustablemode, alignment openings 104 (FIG. 1) are placed over the alignment pins(not illustrated) of chassis 300. At this point line card connectors 103(Optics (LC)) and fabric card connectors 102 (Optics (FC) are in properalignment to be presented to line card connectors 303 and fabric cardconnectors 304 respectively. Housing 100 fits to chassis 300 generallyin the direction of the illustrated directional arrows.

Backplane assembly 100 has a built-in vertical clearance area designedto allow enough room for the router's lower electrical board 305 whenthe optics backplane assembly 100 is installed to chassis 300. This areais illustrated herein by the arrows labeled Clearance for fitting overElectrical Board. Also shown are cooling fans housed in the top andbottom sections of the main router chassis 300. Cooling fans are fordispersing heat generated by processing.

Removal of a Backplane Assembly:

Referring now to FIG. 3, it is again noted herein that each fabric card(306) and line card (302) fits into card cage 301 as previouslydescribed with respect to the main router housing (300) so that themethod of unplugging and disconnecting a card from a mounted backplaneassembly is to simply pull the card out from its slot similar toremoving a modular PC card from a PC slot. To remove the entirebackplane assembly itself from the router chassis, all of the line cardsand fabric cards are physically pulled from their connections to theoptics backplane assembly and can remain aligned in their slots.Backpanel 101 (FIG. 1) is first removed exposing the aligned interfaceportion (“Hardware Locations”, (FIG. 2) of backplane assembly 100. Thefasteners connecting and tightening the alignment interfaces are removedand backplane assembly 100 may be removed from chassis 300.

In one embodiment the back panel does not have to be removed from thebackplane module. In this embodiment strategic openings (notillustrated) are placed through the wall of the back panel that allowaccess to the tightening bolts around the alignment pins such that theymay be removed with, perhaps, a specially designed tool. In stillanother embodiment, a portion of back panel 101 may be hinged such thatthe portion swings open exposing alignment interfaces.

Installing a Backplane Assembly:

Installation of a backplane assembly is essentially reversed fromremoval. Referring back to FIG. 2 the telescopic fasteners of thetwo-piece assembly are loosened to provide float capability for aligningthe alignment pins to the alignment openings 104 of FIG. 1. Openings 104are only slightly oversize from the alignment pins and not enough tocause miss-alignment of connectors as previously described. Once thealignment pins are engaged through openings 104 of assembly 100, thenthe alignment interfaces are tightened and back panel 101 may bereinstalled. At this point the line and fabric cards may be slid backinto their slots and plugged in using suitable force.

In one embodiment backpanel 101 is first removed exposing the alignmentinterface portion of the backplane module. The connecting and alignmentfasteners are then loosed and removed allowing the backplane module tobe removed from the main router chassis.

It will be apparent to the skilled artisan that there are a variety ofalterations that may be made to the embodiments described herein withoutdeparting from the spirit and scope of the invention. For example, inone embodiment, instead of optics ferrules, other known fiber-opticsconnection mechanisms may be utilized to effect backplane connections.

Providing an optics backplane that is modular and adjustable enablesflexibility in maintenance in addition to improved signal transmission.For example, if an optics backplane assembly requires service ortesting, a spare backplane module may be fitted to the host chassis sothat it is not out-of-service while it's backplane assembly is beingserviced. The fiber connections may be simply removed and re-routed aswell enabling quick re-assignment of communication paths forcard-to-card communication.

The present invention may be adapted to routers of same or differentmanufacture. There are many possible embodiments for providing specificand optimal backplane schemes. The method and apparatus of the presentinvention should be afforded the broadest scope under examination. Thespirit and scope of the present invention is limited only by thelanguage of the claims, which follow.

1. A modular and adjustable backplane assembly to provide backplanecommunication between a first and second signal interface and acorresponding first and second set of touter cards in a first packetrouter cabinet to a first and second signal interface and acorresponding first and second set of router cards in a second packetrouter cabinet, comprising: a first portion mounting a third signalinterface configured to engage the first signal interface of the firstpacket router cabinet; a second portion mounting a fourth signalinterface configured to engage the second signal interface of the firstpacket router cabinet; a third portion mounting a fifth signal interfaceconfigured to engage the first signal interface of the second packetrouter cabinet; a fourth portion mounting a sixth signal interfaceconfigured to engage the second signal interface of the second packetrouter cabinet; adjustment mechanisms allowing relative movement betweenthe first and second portions, and the third and fourth portionsrespectively, while preserving the modularity of the backplane assembly;a first signal conductor assembly engaging the third and fourth signalinterfaces to communicate signals between the first set of router cardsand the second set of router cards in the first packet router cabinet; asecond signal conductor assembly engaging the fifth and sixth signalinterfaces to communicate signals between the first set of router cardsand the second set of router cards in the second packet router cabinet;and a seventh signal interface connected to one or both of the third andfourth signal interfaces at the first cabinet; and an eighth signalinterface connected to one or both of the fifth and sixth signalinterfaces of the second cabinet; wherein the seventh signal interfaceis connected to the eighth signal interface enabling router card setshoused in the first packet router cabinet to communicate with the routercard sets housed in the second packet router cabinet thereby providing ascalable router.
 2. The backplane assembly of claim 1 wherein the firstand second signal interfaces in the first and second packet routercabinets are groups of connectors for connecting signal conductors toindividual ones of router cards in the first and second router card setsof each cabinet.
 3. The backplane assembly of claim 1 wherein the firstand second signal interfaces in the first and second packet routercabinets are connectors to printed circuit boards (PCBs) that are inturn connected to the first and second set of router cards in eachcabinet.
 4. The backplane assembly of claim 3 wherein the signalconductor assemblies comprise a cable of electrical conductors havingend-connectors to engage the electrical connectors at the PCBs.
 5. Thebackplane assembly of claim 1 wherein the third, fourth, fifth, sixthand seventh signal interfaces comprise fiber-optic connectors, and thesignal conductor assemblies comprise one or more fiber-optic fibershaving end-connectors for engaging the fiber-optic connectors.
 6. Thebackplane assembly of claim 5 wherein the one or more fibers compriseone or more bundles, ribbons or cables.
 7. The backplane assembly ofclaim 1 wherein the third, fourth, fifth, sixth and seventh signalinterfaces comprise electrical connectors, and the signal conductorassemblies comprise one or more cables of electrical conductors havingend connectors to engage the electrical connectors.
 8. The backplaneassembly of claim 1 wherein the adjustment mechanisms comprisetelescopic engagement elements allowing adjustment of separation betweenthe first and second portions and the third and fourth portionsrespectively.
 9. The backplane assembly of claim 8 wherein theadjustment mechanisms each comprise a locking mechanism for securing thetelescoping first and second portions and third and forth portions afteradjustment to engage the first and second interfaces of each cabinet.